The present invention relates to an analyzer device for analyzing at least one gas contained in a liquid, in particular a drilling liquid, flowing in a drilling pipe in an installation for extracting fluid from a subsoil. The device comprises an analyzer for analyzing the gas and a sampling apparatus for sampling at least a fraction of the gas. The sampling apparatus has at least one porous membrane member, the member comprising a support and having a first face in contact with the liquid flowing in the drilling pipe and a second face opening into a pipe connected to the analyzer.
When drilling a well for oil or some other effluent (in particular gas, steam, water), it is known to analyze the gaseous compounds contained in the drilling muds emerging from the well. Such analysis is used to reconstruct the succession of geological formations through which the borehole is being drilled and it contributes to determining the working possibilities of the fluid deposits encountered.
Such analysis is performed continuously and comprises two main stages. The first stage consists in extracting the gas conveyed by the mud (for example hydrocarbon compounds, carbon dioxide, hydrogen sulfide). The second stage consists in qualifying and quantifying the extracted gases.
For this purpose, mechanically-stirred degassers are frequently used. However, because of their size, such degassers must be installed at a distance from the well, generally close to a vibrating screen downstream from the wellhead. Muds are conveyed from the wellhead to the degasser via a flow line that might be open to the atmosphere. Thus, a fraction of the gaseous compounds present in the mud is released into the atmosphere while the mud is traveling along the line. An analysis of the gas present in the mechanically-stirred degasser is therefore not representative of the gaseous content of the mud in the well.
To solve that problem, devices of the above-specified type have been implanted directly in the drilling pipe, upstream from the wellhead, as described in U.S. Pat. No. 5,469,917. Such devices include a capillary tubular membrane supported capillary membrane (SCMS). However, the muds flowing around the membrane are laden with pieces of rock.
In order to avoid degrading the tubular membrane under the effect of impacts against these pieces of rock, the membrane is wound on a threaded rod. The thread of the support then protects the membrane against pieces of rock of a size greater than the distance between two consecutive threads of the threaded rod.
Those devices do not give entire satisfaction. To wind the membrane around the threaded rod, and thus provide it with protection, certain stresses need to be applied to the membrane. Thus, a membrane of tubular shape must be used in order to be capable of winding between the threads of the threaded rod. Furthermore, the membrane must be relatively flexible. Consequently, only a membrane based on organic materials can be used in such a device. Unfortunately, organic membranes present abilities at withstanding high temperatures and chemical compatibilities that are not always satisfactory in certain applications.